Ultrasonic testing has become a popular method for flaw detection in new, as well as in-service, materials and equipment. Such testing can determine the size and position of most flaws in the material and equipment. These flaws can be surface cracks, imbedded cracks, voids in the material, non-uniform or non-desirable density, and the like. This information has allowed technicians to determine whether the inspected equipment is still in working condition and potentially how long the equipment will remain in working condition.
One industry which has benefitted greatly from ultrasonic testing has been aircraft manufacturing and maintenance. Modern aircraft require high accuracy parts to remain intact during operation, both on the outside and the inside. Such parts may include, but are not limited to, compressor fan blades, turbine fan blades, airfoils, and the like. Flaws in the original manufacture, or due to subsequent damage from use, of such parts could result in the parts not functioning properly and damaging themselves or the rest of the aircraft. Ultrasonic testing allows such potentially harmful flaws to be found before they become dangerous to the aircraft.
Ultrasonic testing begins with a transducer bombarding the object in question with sound waves. When the sound waves come upon a flaw in the object or the opposite side of the object, the wave is reflected. The transducer receives these reflected waves and turns them into an electrical signal. A computer then converts the electrical signals from the transducer into a graph that shows the size and position of the flaw.
Sound waves are transmitted better in some liquids, such as water, than in air. Thus, to increase the sensitivity of the scans, the object in question can be immersed in a tank of water or other suitable medium. The transducer is also submerged to create a waterpath, a path between the transducer and the object through the water.
The transducers are typically held by a transducer holder, which is attached to an actuator by a connection rod. This actuator allows for the transducer holder to be moved in a variety of directions, such as, but not limited to, along an axis parallel to the connection rod and along two axes perpendicular to the connection rod. The actuator may be controlled by a computer operating a pre-programmed algorithm.
While effective, the ultrasonic testing method is limited by the shape of the object being tested. Typically, the object must be relatively planar and not have complicated surface geometry. Additionally, the waterpath needs to remain constant to get consistent readings from the transducers. Clearly a need has arisen for a mechanism that would allow an operator to use ultrasonic testing to scan objects of more complex shape and design, while maintaining a constant waterpath.